全文获取类型
收费全文 | 11764篇 |
免费 | 1136篇 |
国内免费 | 774篇 |
学科分类
工业技术 | 13674篇 |
出版年
2024年 | 42篇 |
2023年 | 142篇 |
2022年 | 285篇 |
2021年 | 357篇 |
2020年 | 372篇 |
2019年 | 274篇 |
2018年 | 279篇 |
2017年 | 338篇 |
2016年 | 362篇 |
2015年 | 407篇 |
2014年 | 671篇 |
2013年 | 657篇 |
2012年 | 767篇 |
2011年 | 855篇 |
2010年 | 656篇 |
2009年 | 679篇 |
2008年 | 655篇 |
2007年 | 755篇 |
2006年 | 718篇 |
2005年 | 682篇 |
2004年 | 524篇 |
2003年 | 515篇 |
2002年 | 475篇 |
2001年 | 428篇 |
2000年 | 353篇 |
1999年 | 275篇 |
1998年 | 195篇 |
1997年 | 219篇 |
1996年 | 156篇 |
1995年 | 142篇 |
1994年 | 101篇 |
1993年 | 57篇 |
1992年 | 57篇 |
1991年 | 46篇 |
1990年 | 41篇 |
1989年 | 30篇 |
1988年 | 18篇 |
1987年 | 13篇 |
1986年 | 20篇 |
1985年 | 10篇 |
1984年 | 8篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1967年 | 2篇 |
1966年 | 2篇 |
1965年 | 2篇 |
1959年 | 16篇 |
1954年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
大型连杆流线简易试验方法 总被引:1,自引:1,他引:0
程里 《理化检验(物理分册)》2004,40(9):457-458
介绍了一种大型连杆流线的简易试验方法及其评价原则。该方法可清晰显示流线,并适合任何尺寸和形状的锻造连杆的流线试验。 相似文献
4.
5.
6.
A problem of deformation of a curved shell loaded by internal pressure, axial force, and temperature difference is discussed. Physical equations are derived whereby the displacements and angles of rotation of the line of centers of mass of cross sections of a shell are related to loading parameters. A general constitutive set of equations for a curved element during its deformation is given. Using a method of initial parameters, an analytical solution is obtained for the differential equations for displacements and angles of rotation of the center line allowing for the action of distributed forces and moments. 相似文献
7.
8.
B. P. PEHRSON J. D. LANDES 《Fatigue & Fracture of Engineering Materials & Structures》2007,30(2):73-86
The purpose of this study is to examine the current standard fracture toughness test procedure to determine if there could be an easier method to get a JIc value from the test record. The current method for determining JIc involves a detailed computational and construction procedure. The objective in this study is to simplify the analysis for the determination of JIc. The results of this study show that the load and displacement record for a fracture toughness test can be used to directly estimate a JQ value, a provisional value for fracture toughness, JIc. The J value taken at the maximum load point can be used along with an adjustment factor to estimate a JQ value. This JQ estimate is close to the one obtained from the construction procedure of ASTM Standard E 1820. When a unit‐sized specimen is tested, that is, a specimen with a width of 50 mm and a thickness of 25 mm the maximum load point provides a direct estimate of JQ. Other sizes require a size adjustment factor, which is simply a square root relationship between the width of the test specimen and a unit width. The proposed new method of estimating JQ is simple in concept and requires a minimum number of calculations. It appears to produce values of JQ which are comparable to those obtained from the ASTM E1820 construction procedure and may produce less scatter. 相似文献
9.
The influence of an aggressive environment (0.6 M, aerated NaCl solution) on short fatigue crack initiation and growth behaviour has been studied. The study involved three major test series, namely: air fatigue, corrosion fatigue, and intermittent air fatigue/corrosion fatigue. The above tests carried out under fully reversed torsional loading conditions at a frequency of 5 Hz, showed that it was the non-metallic inclusions which took part in crack initiation resulting from debonding at metal matrix/inclusion interface and pitting of inclusions in both air and corrosove environments, respectively. Short fatigue crack growth results in these two environments obtained by using plastic replication technique, indicated a large effect of microstructure i.e. prior austenite grain boundaries. The stage/stages at which the environmental contribution was dominant has been discussed by considering the results achieved from intermittent tests. However, the mechanisms involved in corrosion fatigue short crack growth have also been described in the light of results obtained from futher investigations carried out by conducting corrosion fatigue tests under applied cathodic potential conditions and tests on hydrogen pre-charged specimens under air fatigue and uniaxial tension conditions. 相似文献
10.
不同工作制曲柄连杆式飞剪机的设计 总被引:2,自引:0,他引:2
通过对曲柄连杆式飞剪机工作制和工作特点的分析,介绍了不同工作制飞剪机的设计要点,给出了在设计中应遵循的原则,从而使其设计更加合理. 相似文献